Answer:
c) Variable overhead efficiency variance = $320 Unfavorable
Explanation:
The variable overhead efficiency variance is the difference between the actual hours and the standard hours for the actual output valued at the standard variable overhead rate per hour.
Hours
8700 units should have taken (8700× 0.1) 870
but took 910
40 Unfavorable
× Standard rate per hour × $8
Variable overhead efficiency variance $320 Unfavorable
Variable overhead efficiency variance = $320 Unfavorable